Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quem era o treinador principal quando o oponente era o Arsenal?
 ###Tabelas: CREATE TABLE malaysia_xi (malaysia_xi_id AUTO_INCREMENT PRIMARY KEY, Date VARCHAR, Location VARCHAR, Head coach VARCHAR, Opponent VARCHAR, Result VARCHAR) CREATE TABLE appearances__&__goals (appearances__&__goals_id AUTO_INCREMENT PRIMARY KEY, Squad No. INT, Name VARCHAR, Position VARCHAR, League Apps VARCHAR, League Goals INT, FA Cup Apps VARCHAR, FA Cup Goals INT, League Cup Apps VARCHAR, League Cup Goals INT, FLT Apps VARCHAR, FLT Goals INT, Total Apps VARCHAR, Total Goals INT) CREATE TABLE macro-economic_trend (macro-economic_trend_id AUTO_INCREMENT PRIMARY KEY, Year INT, Gross domestic product INT, US dollar exchange VARCHAR, Nominal per-capita GDP (as % of USA) INT, PPP capita GDP (as % of USA) VARCHAR) CREATE TABLE popular_languages_used_for_data_exchange (popular_languages_used_for_data_exchange_id AUTO_INCREMENT PRIMARY KEY, Schemas VARCHAR, Flexible VARCHAR, Semantic verification VARCHAR, Dictionary VARCHAR, Information Model VARCHAR, Synonyms and homonyms VARCHAR, Dialecting VARCHAR, Web standard VARCHAR, Transformations VARCHAR, Lightweight VARCHAR, Human readable VARCHAR) CREATE TABLE repechage_1 (repechage_1_id AUTO_INCREMENT PRIMARY KEY, Rank INT, Rowers VARCHAR, Country VARCHAR, Time VARCHAR, Notes VARCHAR)  
SELECT Head coach FROM malaysia_xi WHERE Opponent = arsenal